Ignore unset properties of V2 Request param classes when making requests (#1796)

* Add some tests

* Fixed V2 request param serialization of unset parameters

* Added a test case for updating a property after initialization

---------

Co-authored-by: Michael Broshi <mbroshi@stripe.com>

Author: prathmesh-stripe

lib/stripe/request_params.rb

@@ -5,11 +5,46 @@ module Stripe
   # For internal use only. Does not provide a stable API and may be broken
   # with future non-major changes.
   class RequestParams
+    class << self
+      # Override the object instantiation flow in Ruby in order to track explicitly set keys
+      # V2 APIs accept null values on the backend. However, we do not want to set a key to nil
+      # if the user has not explicitly set them to nil
+      # TODO(major): https://go/j/DEVSDK-2990
+      def new(**kwargs)
+        instance = allocate
+        # Track explicitly set keys for V2 classes only
+        instance.instance_variable_set(:@_explicitly_set_keys, kwargs.keys.to_set) if name&.start_with?("Stripe::V2::")
+        instance.send(:initialize, **kwargs)
+        instance
+      end
+
+      # Override attr_accessor to create setters that track explicitly set keys for V2 classes
+      def attr_accessor(*names)
+        names.each do |name|
+          # Define getter
+          define_method(name) { instance_variable_get("@#{name}") }
+
+          # Define setter that tracks the key as explicitly set
+          define_method("#{name}=") do |value|
+            @_explicitly_set_keys&.add(name)
+            instance_variable_set("@#{name}", value)
+          end
+        end
+      end
+    end
+
     def to_h
       instance_variables.each_with_object({}) do |var, hash|
+        # _explicitly_set_keys is set as an instance variable.
+        # Ignore the var if it is _explicitly_set_keys itself.
+        next if var == :@_explicitly_set_keys
+
         key = var.to_s.delete("@").to_sym
         value = instance_variable_get(var)
 
+        # For V2 classes, only include keys that were explicitly set
+        next if @_explicitly_set_keys && !@_explicitly_set_keys.include?(key)
+
         hash[key] = if value.is_a?(RequestParams)
                       value.to_h
                     # Check if value is an array and contains RequestParams objects

test/stripe/request_params_test.rb

@@ -269,5 +269,77 @@ def initialize(games: nil)
         assert_equal expected, params.to_h
       end
     end
+
+    context "V2 RequestParams explicit key tracking" do
+      should "only serialize explicitly set fields for V2 classes" do
+        params = Stripe::V2::Billing::MeterEventCreateParams.new(
+          event_name: "my_event",
+          payload: { stripe_customer_id: "cus_123", value: "25" }
+        )
+
+        result = params.to_h
+
+        assert_equal "my_event", result[:event_name]
+        assert_equal({ stripe_customer_id: "cus_123", value: "25" }, result[:payload])
+        refute result.key?(:identifier), "identifier was not set and should not be in the hash"
+        refute result.key?(:timestamp), "timestamp was not set and should not be in the hash"
+      end
+
+      should "serialize fields explicitly set to nil for V2 classes" do
+        params = Stripe::V2::Billing::MeterEventCreateParams.new(
+          event_name: "my_event",
+          identifier: nil,
+          payload: { stripe_customer_id: "cus_123", value: "25" }
+        )
+
+        result = params.to_h
+
+        assert_equal "my_event", result[:event_name]
+        assert result.key?(:identifier), "identifier was explicitly set to nil and should be in the hash"
+        assert_nil result[:identifier]
+        assert_equal({ stripe_customer_id: "cus_123", value: "25" }, result[:payload])
+        refute result.key?(:timestamp), "timestamp was not set and should not be in the hash"
+      end
+
+      should "serialize fields explicitly set after initialization for V2 classes" do
+        params = Stripe::V2::Billing::MeterEventCreateParams.new(
+          event_name: "my_event",
+          payload: { stripe_customer_id: "cus_123", value: "25" }
+        )
+
+        params.identifier = "Something"
+        params.timestamp = nil
+
+        result = params.to_h
+
+        assert_equal "my_event", result[:event_name]
+        assert_equal "Something", result[:identifier]
+        assert_equal({ stripe_customer_id: "cus_123", value: "25" }, result[:payload])
+        assert result.key?(:timestamp)
+        assert_nil result[:timestamp]
+      end
+
+      should "serialize all fields even if some fields are set after initialization for V1 classes" do
+        params = FooCreateParams.new
+
+        params.fun = "games"
+
+        result = params.to_h
+
+        assert_equal "games", result[:fun]
+        assert result.key?(:team), "V1 classes should include all fields even if not explicitly set"
+        assert_nil result[:team]
+      end
+
+      should "serialize all fields including nil defaults for V1 classes" do
+        params = FooCreateParams.new(fun: "games")
+
+        result = params.to_h
+
+        assert_equal "games", result[:fun]
+        assert result.key?(:team), "V1 classes should include all fields even if not explicitly set"
+        assert_nil result[:team]
+      end
+    end
   end
 end